RCD on sub mains....

[rob_sparkie]

hi there, i am working in a muliple occupation house and there are existing sub mains to each room. i am bringing it up to standards but im not 100% on one subject.

the sub mains are already wired in twin and earth from isolators from the intake area, since i cannot follow their route exactly i will accept that they might be within 50mm in walls ..etc.. this will mean i should cover them by a 30m/a RCD. this is fine but will i have to upgrade the existing consumer units in each room to a 17th edition with 2 RCD's? since its covered by the sub main isolator/rcd, or can you get a 30 m/a time delay rcd to stop both of them tripping inconveniently.

thanks for your comments...

 

[Spudnik]

No.

As its HMO all you need do is protect each submain with its own RCD so that if it does trip, it wont take out any other rooms.

 

[havoone]

No.

As its HMO all you need do is protect each submain with its own RCD so that if it does trip, it wont take out any other rooms.

only problem i see here is division of installation. whereby a fault on one circuit will cut power to the whole installation within a dwelling, so it may be better to upgrade the consumer units to 17th edition and install time delays at origin of each submain. another point is, can the tenants get access to the sub main RCD to reconnect after a fault/ or to test quarterly.